feat: Porting PadLeft and PadRight from C#

src/Core/Rexl.Bind/Operations/BuiltinFunctions.cs

@@ -378,6 +378,11 @@ private BuiltinFunctions()
         AddOne(TextTrimFunc.TrimStart, new Sig(S.AboutTrimStart, A.Create(S.ArgSource, S.AboutTrimStart_Source)));
         AddOne(TextTrimFunc.TrimEnd, new Sig(S.AboutTrimEnd, A.Create(S.ArgSource, S.AboutTrimEnd_Source)));
 
+        AddOne(TextPadFunc.PadCenter, new Sig(S.AboutPadCenter, A.Create(S.ArgSource, S.AboutPad_Source), A.Create(S.ArgLength, S.AboutPad_Len)));
+        AddOne(TextPadFunc.PadCenter, "PadCenter");
+        AddOne(TextPadFunc.PadStart, new Sig(S.AboutPadStart, A.Create(S.ArgSource, S.AboutPad_Source), A.Create(S.ArgLength, S.AboutPad_Len)));
+        AddOne(TextPadFunc.PadEnd, new Sig(S.AboutPadEnd, A.Create(S.ArgSource, S.AboutPad_Source), A.Create(S.ArgLength, S.AboutPad_Len)));
+
         AddOne(TextReplaceFunc.Instance, new Sig(S.AboutTextReplace,
             A.Create(S.ArgSource, S.AboutTextReplace_Source),
             A.Create(S.TextReplace_Remove, S.AboutTextReplace_Remove),

src/Core/Rexl.Bind/Operations/Funcs/Text.cs

@@ -758,3 +758,141 @@ public static string Exec(string src, string remove, string insert)
         return src.Replace(remove, insert);
     }
 }
+
+/// <summary>
+/// Functions to add padding to either end of a string.
+/// The center version (PadCenter) will add spaces to both ends of the given string.
+/// The start version (PadStart) will add spaces to the start of the given string.
+/// The end version (PadEnd) will add spaces to the end of the given string.
+/// </summary>
+public sealed partial class TextPadFunc : RexlOper
+{
+    public enum PadKind : byte
+    {
+        // Center justification, pad both ends of the string
+        Center,
+        // Pad the start of the string.
+        Start,
+        // Pad the end of the string.
+        End
+    }
+
+    public static readonly TextPadFunc PadCenter = new TextPadFunc(PadKind.Center, "Pad");
+    public static readonly TextPadFunc PadStart = new TextPadFunc(PadKind.Start, "PadStart");
+    public static readonly TextPadFunc PadEnd = new TextPadFunc(PadKind.End, "PadEnd");
+
+    public PadKind Kind { get; }
+
+    public Func<string, long, string> Map { get; }
+
+    private TextPadFunc(PadKind kind, string name)
+        : base(isFunc: true, new DName(name), BindUtil.TextNs, 2, 2)
+    {
+        switch (kind)
+        {
+        case PadKind.Start:
+            Map = ExecStart;
+            break;
+        case PadKind.End:
+            Map = ExecEnd;
+            break;
+        default:
+            Validation.Assert(kind == PadKind.Center);
+            Map = ExecCenter;
+            break;
+        }
+
+        Kind = kind;
+    }
+
+    protected override ArgTraits GetArgTraitsCore(int carg)
+    {
+        Validation.Assert(SupportsArity(carg));
+        var maskAll = BitSet.GetMask(carg);
+        var maskOpt = maskAll.ClearBit(0);
+        return ArgTraitsLifting.Create(this, carg, maskLiftSeq: maskAll, maskLiftTen: maskAll, maskLiftOpt: maskOpt);
+    }
+
+    protected override (DType, Immutable.Array<DType>) SpecializeTypesCore(InvocationInfo info)
+    {
+        Validation.AssertValue(info);
+        Validation.Assert(SupportsArity(info.Arity));
+        Validation.Assert(info.Arity == 2);
+
+        return (DType.Text, Immutable.Array.Create(DType.Text, DType.I8Req));
+    }
+
+    protected override bool CertifyCore(BndCallNode call, ref bool full)
+    {
+        if (call.Type != DType.Text)
+            return false;
+        var args = call.Args;
+        if (args[0].Type != DType.Text)
+            return false;
+        if (args[1].Type != DType.I8Req)
+            return false;
+        return true;
+    }
+
+    protected override BoundNode ReduceCore(IReducer reducer, BndCallNode call)
+    {
+        Validation.AssertValue(reducer);
+        Validation.Assert(IsValidCall(call));
+
+        var lenArg = call.Args[1];
+        if (lenArg.TryGetI8(out var len))
+        {
+            var srcArg = call.Args[0];
+            if (len <= 0)
+                return srcArg;
+            if (srcArg.TryGetString(out var str))
+            {
+                if (Util.Size(str) >= len)
+                    return srcArg;
+                return BndStrNode.Create(Map(str, len));
+            }
+        }
+
+        return call;
+    }
+
+    public static string ExecCenter(string src, long len)
+    {
+        if (len <= 0)
+            return src;
+        int count = (int)Math.Min(len, int.MaxValue);
+        if (string.IsNullOrEmpty(src))
+            return new string(' ', count);
+        if (count <= src.Length)
+            return src;
+        return string.Create(count, src.AsMemory(), static (dst, mem) =>
+        {
+            int spaces = (dst.Length - mem.Length) / 2;
+
+            if (spaces > 0)
+                dst.Slice(0, spaces).Fill(' ');
+            mem.Span.CopyTo(dst.Slice(spaces, mem.Length));
+            dst.Slice(spaces + mem.Length).Fill(' ');
+        });
+    }
+
+    public static string ExecStart(string src, long len)
+    {
+        if (len <= 0)
+            return src;
+        int count = (int)Math.Min(len, int.MaxValue);
+        if (string.IsNullOrEmpty(src))
+            return new string(' ', count);
+        return src.PadLeft(count);
+    }
+
+    public static string ExecEnd(string src, long len)
+    {
+        if (len <= 0)
+            return src;
+        int count = (int)Math.Min(len, int.MaxValue);
+        if (string.IsNullOrEmpty(src))
+            return new string(' ', count);
+        return src.PadRight(count);
+    }
+}

src/Core/Rexl.Bind/Strings/RexlStrings.cs

@@ -29,6 +29,7 @@ static partial class RexlStrings
     public static readonly StringId ArgX = new(nameof(ArgX), "x");
     public static readonly StringId ArgY = new(nameof(ArgY), "y");
     public static readonly StringId ArgAngle = new(nameof(ArgAngle), "angle");
+    public static readonly StringId ArgLength = new(nameof(ArgLength), "length");
 
     public static readonly StringId AboutArgSeqSource = new(nameof(AboutArgSeqSource), "The source sequence.");
     public static readonly StringId AboutArgPredicate = new(nameof(AboutArgPredicate), "The condition with which to test an item.");
@@ -342,6 +343,12 @@ static partial class RexlStrings
     public static readonly StringId AboutUpper = new(nameof(AboutUpper), "Converts text to uppercase.");
     public static readonly StringId AboutUpper_Source = new(nameof(AboutUpper_Source), "The text to convert to uppercase.");
 
+    public static readonly StringId AboutPadCenter = new(nameof(AboutPadCenter), "Adds spaces to both ends of the given text so the result is of the given length.");
+    public static readonly StringId AboutPadStart = new(nameof(AboutPadStart), "Adds spaces to the start of the given text so the result is of the given length.");
+    public static readonly StringId AboutPadEnd = new(nameof(AboutPadEnd), "Adds spaces to the end of the given text so the result is of the given length.");
+    public static readonly StringId AboutPad_Source = new(nameof(AboutPad_Source), "The text to add padding to.");
+    public static readonly StringId AboutPad_Len = new(nameof(AboutPad_Len), "The minimum length of the text after padding.");
+
     public static readonly StringId AboutStartsWith = new(nameof(AboutStartsWith), "Tests whether the beginning of the source text matches the lookup text.");
     public static readonly StringId AboutStartsWith_Source = new(nameof(AboutStartsWith_Source), "The text to look in.");
     public static readonly StringId AboutStartsWith_LookUp = new(nameof(AboutStartsWith_LookUp), "The text to look for.");

src/Core/Rexl.Bind/Strings/RexlStrings.tt

@@ -23,6 +23,7 @@ ArgValue = "value"
 ArgX = "x"
 ArgY = "y"
 ArgAngle = "angle"
+ArgLength = "length"
 
 AboutArgSeqSource = "The source sequence."
 AboutArgPredicate = "The condition with which to test an item."
@@ -336,6 +337,12 @@ AboutLower_Source = "The text to convert to lowercase."
 AboutUpper = "Converts text to uppercase."
 AboutUpper_Source = "The text to convert to uppercase."
 
+AboutPadCenter = "Adds spaces to both ends of the given text so the result is of the given length."
+AboutPadStart = "Adds spaces to the start of the given text so the result is of the given length."
+AboutPadEnd = "Adds spaces to the end of the given text so the result is of the given length."
+AboutPad_Source = "The text to add padding to."
+AboutPad_Len = "The minimum length of the text after padding."
+
 AboutStartsWith = "Tests whether the beginning of the source text matches the lookup text."
 AboutStartsWith_Source = "The text to look in."
 AboutStartsWith_LookUp = "The text to look for."

src/Core/Rexl.Code/Operations/BuiltinGenerators.cs

@@ -59,6 +59,7 @@ private BuiltinGenerators()
         Add(TextPartGen.Instance);
         Add(TextTrimGen.Instance);
         Add(TextReplaceGen.Instance);
+        Add(TextPadGen.Instance);
 
         Add(typeof(SumFunc), SumBaseGen.Instance);
         Add(typeof(MeanFunc), SumBaseGen.Instance);

src/Core/Rexl.Code/Operations/Funcs/Text.cs

@@ -293,3 +293,22 @@ protected override bool TryGetMeth(ICodeGen codeGen, BndCallNode call, out Metho
         return true;
     }
 }
+
+public sealed class TextPadGen : GetMethGen<TextPadFunc>
+{
+    public static readonly TextPadGen Instance = new TextPadGen();
+
+    private TextPadGen()
+    {
+    }
+
+    protected override bool TryGetMeth(ICodeGen codeGen, BndCallNode call, out MethodInfo meth)
+    {
+        Validation.AssertValue(codeGen);
+        Validation.Assert(IsValidCall(call, true));
+
+        var fn = GetOper(call);
+        meth = fn.Map.Method;
+        return true;
+    }
+}

src/Test/Rexl.Bind.Test/Scripts/Binder/Functions/String.txt

@@ -238,6 +238,43 @@ Text.Replace("ABC", "X", s)
 Text.Replace("ABC", "B", "X")
 Text.Replace("ABACDAE", "A", "!!")
 
+Text.PadStart(s, i8)
+Text.PadStart(null, 0)
+Text.PadStart("hello", -1)
+Text.PadStart(s, -1)
+Text.PadStart("hello", 10)
+Text.PadStart(s, 10)
+Text.PadStart(s, s)
+Text.PadStart(s, u2)
+Text.PadStart(s, qi8)
+Text.PadStart(s, qu2)
+Text.PadStart(i8, i8)
+
+Text.PadEnd(s, i8)
+Text.PadEnd(null, 0)
+Text.PadEnd("hello", -1)
+Text.PadEnd(s, -1)
+Text.PadEnd("hello", 10)
+Text.PadEnd(s, 10)
+Text.PadEnd(s, s)
+Text.PadEnd(s, u2)
+Text.PadEnd(s, qi8)
+Text.PadEnd(s, qu2)
+Text.PadEnd(i8, i8)
+
+Tex.Pad(s, i8)
+Text.PadCenter(s, i8)
+Text.Pad(null, 15)
+Text.Pad("hello", -1)
+Text.Pad(s, -1)
+Text.Pad("hello", 10)
+Text.Pad(s, 10)
+Text.Pad(s, s)
+Text.Pad(s, u2)
+Text.Pad(s, qi8)
+Text.Pad(s, qu2)
+Text.Pad(i8, i8)
+
 // Lifting.
 :: {g:g*, o:o*, s:s*, b:b*, qb:b?*, d:d*, n:n*, qn:n?*, r8:r8*, qr8:r8?*, r4:r4*, qr4:r4?*, i:i*, qi:i?*, i8:i8*, qi8:i8?*, i4:i4*, qi4:i4?*, i2:i2*, qi2:i2?*, i1:i1*, qi1:i1?*, u8:u8*, qu8:u8?*, u4:u4*, qu4:u4?*, u2:u2*, qu2:u2?*, u1:u1*, qu1:u1?*}
 
@@ -360,3 +397,51 @@ Text.Replace("ABC", s, s)
 Text.Replace(s, s, s)
 
 Text.Replace(s, "", s)
+
+Text.PadStart(s, i8)
+Text.PadStart(null, 0)
+Text.PadStart("hello", -1)
+Text.PadStart("hello", [3, 4, 1])
+Text.PadStart(s, [3, 4, 1])
+Text.PadStart(s, -1)
+Text.PadStart("hello", 10)
+Text.PadStart(["hello", "howdy", null], 10)
+Text.PadStart(s, 10)
+Text.PadStart(s, s)
+Text.PadStart(s, u1)
+Text.PadStart(s, u2)
+Text.PadStart(s, u4)
+Text.PadStart(s, u8)
+Text.PadStart(s, qi8)
+Text.PadStart(s, qu2)
+
+Text.PadEnd(s, i8)
+Text.PadEnd(null, 0)
+Text.PadEnd(s, -1)
+Text.PadEnd(s, [3, 4, 1])
+Text.PadEnd("hello", [3, 4, 9])
+Text.PadEnd(["hello", "howdy", null], 10)
+Text.PadEnd(s, 10)
+Text.PadEnd(s, s)
+Text.PadEnd(s, u1)
+Text.PadEnd(s, u2)
+Text.PadEnd(s, u4)
+Text.PadEnd(s, u8)
+Text.PadEnd(s, qi8)
+Text.PadEnd(s, qu2)
+
+Text.PadCenter(s, i8)
+Text.PadCenter(null, 0)
+Text.PadCenter("hello", -1)
+Text.PadCenter("hello", [3, 4, 9])
+Text.PadCenter(s, -1)
+Text.PadCenter(s, [3, 4, 1])
+Text.PadCenter(["hello", "howdy", null], 10)
+Text.PadCenter(s, 10)
+Text.PadCenter(s, s)
+Text.PadCenter(s, u1)
+Text.PadCenter(s, u2)
+Text.PadCenter(s, u4)
+Text.PadCenter(s, u8)
+Text.PadCenter(s, qi8)
+Text.PadCenter(s, qu2)

src/Test/Rexl.Code.Test/Scripts/CodeGen/Functions/String.txt

@@ -1,6 +1,6 @@
 ::: {g:g, o:o, s:s, b:b, qb:b?, d:d, qd:d?, n:n, qn:n?, r8:r8, qr8:r8?, r4:r4, qr4:r4?, i:i, qi:i?, i8:i8, qi8:i8?, i4:i4, qi4:i4?, i2:i2, qi2:i2?, i1:i1, qi1:i1?, u8:u8, qu8:u8?, u4:u4, qu4:u4?, u2:u2, qu2:u2?, u1:u1, qu1:u1?}
 
-``` N := First([null, "hello"]);
+``` N := Null("hello");
 
 Text.Part(Wrap(""), 0)
 Text.Part(Wrap(""), 1)
@@ -71,3 +71,20 @@ Text.TrimEnd(Wrap(Null(""))) | With(_, {S: it, L: Text.Len(it)})
 Text.Replace(N, "A", "B")
 Text.Replace("A", N, "B")
 Text.Replace("ABC", Wrap("B"), N)
+
+Text.PadStart(N, 0)
+Text.PadStart(N, Wrap(10))
+Text.PadStart("hello", Wrap(-1))
+Text.PadStart("hello", Wrap(10))
+
+Text.PadEnd(N, 0)
+Text.PadEnd(N, Wrap(10))
+Text.PadEnd("hello", -1)
+Text.PadEnd("hello", 10)
+Text.PadEnd(Wrap("hello"), 10)
+
+Text.Pad(N, 0)
+Text.Pad(N, Wrap(10))
+Text.PadCenter("hello", -1)
+Text.Pad("hello", 10)
+Text.Pad(Wrap("hello"), 10)