feat: minimal, single digit, int lexer

src/01_lexic/root.zig

@@ -0,0 +1,52 @@
+const std = @import("std");
+const t = std.testing;
+
+const TokenType = enum {
+    Int,
+    Float,
+};
+
+const Token = struct {
+    value: []const u8,
+    token_type: TokenType,
+    start_pos: usize,
+
+    pub fn init(value: []const u8, token_type: TokenType, start: usize) Token {
+        return Token{
+            .value = value,
+            .token_type = token_type,
+            .start_pos = start,
+        };
+    }
+};
+
+pub fn tokenize(input: []const u8) !void {
+    const next_token = try number(input, 0);
+    _ = next_token;
+
+    std.debug.print("tokenize :D {s}\n", .{input});
+}
+
+fn number(input: []const u8, start: usize) !?Token {
+    const first_char = input[start];
+    if (!is_digit(first_char)) {
+        return null;
+    }
+
+    return Token.init(input[start .. start + 1], TokenType.Int, start);
+}
+
+fn is_digit(c: u8) bool {
+    return '0' <= c and c <= '9';
+}
+
+test "number lexer" {
+    const input = "3";
+    const result = try number(input, 0);
+
+    if (result) |r| {
+        try std.testing.expectEqual("3", r.value);
+    } else {
+        try std.testing.expect(false);
+    }
+}

src/main.zig

@@ -1,11 +1,10 @@
 const std = @import("std");
+const lexic = @import("./01_lexic/root.zig");
+
 const thp_version: []const u8 = "0.0.0";
 
 pub fn main() !void {
     try repl();
-
-    // Prints to stderr (it's a shortcut based on `std.io.getStdErr()`)
-    std.debug.print("All your {s} are belong to us.\n", .{"codebase"});
 }
 
 fn repl() !void {
@@ -14,6 +13,18 @@ fn repl() !void {
     const stdout = bw.writer();
     try stdout.print("The THP REPL, v{s}\n", .{thp_version});
     try stdout.print("Enter expressions to evaluate. Enter CTRL-D to exit.\n", .{});
+    try bw.flush();
+
+    const stdin = std.io.getStdIn().reader();
+
+    try stdout.print("\nthp => ", .{});
+    try bw.flush();
+
+    const bare_line = try stdin.readUntilDelimiterAlloc(std.heap.page_allocator, '\n', 8192);
+    defer std.heap.page_allocator.free(bare_line);
+    const line = std.mem.trim(u8, bare_line, "\r");
+
+    try lexic.tokenize(line);
 
     try bw.flush();
 }