Potential syntax for bounded loops (2026 proposal)

[mr-zwets]

There is a bounded loops proposal for BCH.

It would be good to consider the possible syntax this would translate to in CashScript.
The bounded loops construction enables indefinite loops, which can easily emulate definite loops.

From the spec:

Naming and Semantics

This proposal is influenced by the BEGIN ... UNTIL indefinite loop construction in the Forth programming language (upon which the rest of the Bitcoin Cash VM is based). This particular construction offers maximal flexibility: definite loops can be easily emulated with indefinite loops, but indefinite loops cannot be emulated with definite loops.

So there would both be a for and a while loop syntax.
I got the solidity syntax for both, I think they're the same as in Javascript:

while (i != 0) {
    // do something
}

for (uint i = 1; i <= 5; i++) {
    // do something
}

[mr-zwets]

Extra notes: CashScript currently does not have a shorthand increment operator ++ but besides that the solidity syntax of for loops should work as is.

We might want to investigate a simpler syntax for looping x times where x can be a number or a variable like tx.outputs.length

If we don't mind deviating from solidity we could add syntax like:

for i in range(tx.outputs.length) {
    // Access tx.outputs[i]
}

[mr-zwets]

Looping Control

If we add looping, we also need to think about looping control with break and continue

here is solidity's looping control:

https://www.tutorialspoint.com/solidity/solidity_loop_control.htm

Looping Syntax Comparison Table

Some brainstorming with AI on new for-loop syntax, for the solidity-draft proposal it referring to ethereum/solidity#10162

Feature	Python-style for i in range(n)	Solidity-draft for (int value: array)	Traditional for Loop for (int i = 0; i < n; i++)	JS-style for...of for (int value of array)	JS-style forEach array.forEach((value, i) => {...})
CashScript Syntax	for int i in range(n) {}	for (int value: array) {}	for (int i = 0; i < n; i = i + 1) {}	for (int value of array) {}	array.forEach((int value, int i) => { ... })
Member Easily Accessible	❌ No	✅ Yes	✅ Yes	✅ Yes	✅ Yes (via callback argument)
Index Easily Accessible	✅ Yes	❌ No	✅ Yes	❌ No	✅ Yes (via callback argument)
Solidity-like Syntax	❌ No	❌ No (not yet in Solidity)	✅ Yes	❌ No	❌ No (callback-based)
JS-like Syntax	❌ No	❌ No	✅ Yes	✅ Yes	✅ Yes (callbacks are common in JS)
Ease of Use	✅ Very easy	✅ Very easy	❌ More verbose	✅ Very easy	❌ Requires callback
Avoids New Concepts	❌ No (range is new)	❌ No (: is new in CashScript)	❌ No (++, -- are new)	✅ Yes	❌ No (callback functions are new)
Can Iterate in Reverse	✅ Yes (range(n, 0, -1))	❌ No (not built-in)	✅ Yes (for (int i = n; i >= 0; i--))	❌ No (requires workaround)	❌ No (needs .reverse())
Can Iterate in Custom Jumps	✅ Yes (range(start, stop, step))	❌ No (not built-in)	✅ Yes (i += step)	❌ No (requires workaround)	❌ No (requires custom logic in callback)

Chat GPT's conclusion:

Best combination: Implementing a standard for loop and JS-style for...of (instead of Solidity’s draft : syntax) keeps things intuitive. Adding range(n) is optional for simplicity in definite loops.