如何在Squeak(Smalltalk)中用正则表达式检查方法参数数量？

Got it, let's break this down for your compile:where: method. In Squeak, working with regular expressions to count those parameter colon patterns (like first:) is straightforward once you know the right tools—here's a step-by-step solution tailored to your needs:

1. Squeak正则表达式基础 #

Squeak uses its own regex engine, centered around the RxParser class. For your use case, we'll compile a regex pattern that matches parameter names followed by a colon, then count how many times it appears in your input string.

2. 实现参数数量统计与验证 #

First, let's write the code to count the parameters and check if their count matches the argTypeCollection size. Here's how to integrate this into your method:

compile: stringCode where: argTypeCollection
    | paramPattern signaturePart matches paramCount |
    "Compile the regex pattern to match parameter names (e.g., first:, second:)"
    paramPattern := RxParser parse: '[a-zA-Z][a-zA-Z0-9]*:'.
    
    "Extract only the method signature part (before the first |) to avoid matching method body patterns"
    signaturePart := stringCode copyUpTo: $|.
    
    "Find all matches of the parameter pattern in the signature"
    matches := paramPattern matchesIn: signaturePart.
    paramCount := matches size.
    
    "Validate parameter count matches the type collection size"
    paramCount = argTypeCollection size ifFalse: [
        self error: ('Parameter count mismatch: expected {1}, got {2}' 
            format: {argTypeCollection size. paramCount})
    ].
    
    "Add your further analysis/compilation logic here..."

关键细节说明： #

• Regex Pattern: [a-zA-Z][a-zA-Z0-9]*: matches any sequence starting with a letter, followed by any combination of letters/numbers, ending with a colon—exactly the format of your method parameters.
• Signature Extraction: By using copyUpTo: $|, we only check the part of the string before the first vertical bar, which ensures we don't accidentally match similar patterns in the method's local variables or body.
• Counting Matches: matchesIn: returns a collection of all matching substrings, so matches size gives us the exact number of parameters.

3. 测试你的示例 #

Using your sample input:

C compile: 'first: i second: any third: n | local | local := i + n. ^(local*local)' where: #(Integer nil Number)

The code will extract 'first: i second: any third: n ' as the signature part, find 3 matches (first:, second:, third:), and confirm this matches the size of #(Integer nil Number) (3), so it proceeds without error.

内容的提问来源于stack exchange，提问作者Guy Sadoun