feat(fstring): add alignment

examples/basic/23_format_spec.peb

@@ -45,4 +45,15 @@ print(f"{d2:e}")
 print(f"{0:e}")
 print()
 
+print("Alignment")
+print(f"{"test":10}")
+print(f"{"test":<10}")
+print(f"{"test":>10}")
+print(f"{"test":^10}")
+print()
+print(f"{"test":<<9}")
+print(f"{"test":>>9}")
+print(f"{"test":^^9}")
+print()
+
 print("Complex")

src/core/format_spec/lexer.py

@@ -77,6 +77,12 @@ class FormatSpecLexer:
     def scan_token(self):
         char: str = self.advance()
         match char:
+            case "<":
+                self.add_token(TokenType.LEFT)
+            case ">":
+                self.add_token(TokenType.RIGHT)
+            case "^":
+                self.add_token(TokenType.CENTER)
             case "+":
                 self.add_token(TokenType.PLUS)
             case "-":
@@ -111,7 +117,7 @@ class FormatSpecLexer:
                 if char.isdigit():
                     self.scan_number()
                 else:
-                    self.error("Unexpected character")
+                    self.add_token(TokenType.CHAR)
         return None
 
     def scan_number(self):

src/core/format_spec/parser.py

@@ -1,7 +1,7 @@
 from typing import Optional
 
 from src.core.format_spec.spec import FormatSpec, FormatSpecOptions, FormatSpecNumber, FormatSpecIntegral, \
-    FormatSpecDecimal
+    FormatSpecDecimal, FormatSpecAlignment
 from src.core.format_spec.token import Token, TokenType
 from src.parser.error import ParsingError
 from src.pebble import Pebble
@@ -20,6 +20,18 @@ class FormatSpecParser:
         TokenType.T_PCT,
     }
 
+    ALIGNMENT: set[TokenType] = {
+        TokenType.LEFT,
+        TokenType.RIGHT,
+        TokenType.CENTER
+    }
+
+    SIGN: set[TokenType] = {
+        TokenType.PLUS,
+        TokenType.MINUS,
+        TokenType.SPACE
+    }
+
     def __init__(self, tokens: list[Token]):
         self.tokens: list[Token] = tokens
         self.current: int = 0
@@ -68,22 +80,43 @@ class FormatSpecParser:
     def spec(self) -> FormatSpec:
         options: FormatSpecOptions = self.options()
         number: FormatSpecNumber = self.number()
-        type: Optional[Token] = self.type()
+        fmt_type: Optional[Token] = self.type()
         return FormatSpec(
             options=options,
             number=number,
-            type=type
+            type=fmt_type
         )
 
     def options(self) -> FormatSpecOptions:
+        alignment: Optional[FormatSpecAlignment] = self.alignment()
         sign: Optional[Token] = None
-        if self.match(TokenType.PLUS, TokenType.MINUS, TokenType.SPACE):
+        if self.match(*self.SIGN):
             sign = self.previous()
 
         return FormatSpecOptions(
+            alignment=alignment,
             sign=sign
         )
 
+    def alignment(self) -> Optional[FormatSpecAlignment]:
+        if not self.match(TokenType.CHAR, *self.ALIGNMENT):
+            return None
+        fill: Optional[Token] = None
+        align: Token = self.previous()
+
+        if self.match(*self.ALIGNMENT):
+            fill = align
+            align = self.previous()
+
+        if align.type not in self.ALIGNMENT:
+            self.error(align, "Fill character without alignment.")
+            return None
+
+        return FormatSpecAlignment(
+            fill=fill,
+            align=align
+        )
+
     def number(self) -> FormatSpecNumber:
         integral: FormatSpecIntegral = self.integral()
         decimal: Optional[FormatSpecDecimal] = self.decimal()

src/core/format_spec/spec.py

@@ -4,8 +4,15 @@ from typing import Optional
 from src.core.format_spec.token import Token
 
 
+@dataclass(frozen=True)
+class FormatSpecAlignment:
+    fill: Optional[Token]
+    align: Optional[Token]
+
+
 @dataclass(frozen=True)
 class FormatSpecOptions:
+    alignment: Optional[FormatSpecAlignment]
     sign: Optional[Token]
 
 

src/core/format_spec/string_formatter.py

@@ -1,7 +1,7 @@
 from math import log10, floor
 from typing import Any, Optional
 
-from src.core.format_spec.spec import FormatSpec
+from src.core.format_spec.spec import FormatSpec, FormatSpecAlignment
 from src.core.format_spec.token import TokenType, Token
 from src.interpreter.error import PebbleRuntimeError
 
@@ -69,6 +69,8 @@ class StringFormatter:
         else:
             fmt_type, obj = self.guess_type(obj)
 
+        align_side: TokenType = TokenType.LEFT
+        fill_char: str = " "
         match fmt_type:
             case None:
                 res = self.stringify(obj)
@@ -76,15 +78,25 @@ class StringFormatter:
                 res = obj
             case TokenType.T_BIN | TokenType.T_DEC | TokenType.T_HEX | TokenType.T_HEX_CAPS | TokenType.T_OCT:
                 res = self.format_int(obj, spec, fmt_type)
+                align_side = TokenType.RIGHT
             case TokenType.T_FIX:
                 res = self.format_float_fix(obj, spec, fmt_type)
+                align_side = TokenType.RIGHT
             case TokenType.T_PCT:
                 res = self.format_float_fix(obj * 100, spec, TokenType.T_FIX) + "%"
+                align_side = TokenType.RIGHT
             case TokenType.T_SCI:
                 res = self.format_float_sci(obj, spec, fmt_type)
+                align_side = TokenType.RIGHT
+
+        align_spec: Optional[FormatSpecAlignment] = spec.options.alignment
+        if align_spec is not None:
+            align_side = align_spec.align.type
+            if align_spec.fill is not None:
+                fill_char = align_spec.fill.lexeme
 
         if spec.number.integral.width is not None:
-            res = self.pad(res, spec.number.integral.width)
+            res = self.pad(res, spec.number.integral.width, align_side, fill_char)
         return res
 
     def format_int(self, value: int, spec: FormatSpec, fmt_type: TokenType) -> str:
@@ -168,8 +180,21 @@ class StringFormatter:
             groups.append(string[max(0, length - i - group_size):length - i])
         return sep.join(reversed(groups))
 
-    def pad(self, string: str, width: int) -> str:
+    def pad(self, string: str, width: int, side: TokenType, char: str) -> str:
         to_pad: int = width - len(string)
-        if to_pad > 0:
+        if to_pad <= 0:
-            string = " " * to_pad + string
+            return string
-        return string
+        left: int = 0
+        right: int = 0
+        match side:
+            case TokenType.LEFT:
+                left = 0
+                right = to_pad
+            case TokenType.RIGHT:
+                left = to_pad
+                right = 0
+            case TokenType.CENTER:
+                left = to_pad // 2
+                right = to_pad - left
+
+        return char * left + string + char * right

src/core/format_spec/token.py

@@ -6,6 +6,11 @@ from src.core.position import Position
 
 
 class TokenType(Enum):
+    # Align
+    LEFT = auto()
+    RIGHT = auto()
+    CENTER = auto()
+
     # Sign
     PLUS = auto()
     MINUS = auto()
@@ -35,6 +40,7 @@ class TokenType(Enum):
     NUMBER = auto()
     DOT = auto()
     EOF = auto()
+    CHAR = auto()
 
 
 @dataclass(frozen=True)