Implement input(prompt)

[kmr-srbh]

No description provided.

[kmr-srbh]

@Shaikh-Ubaid , there is a small issue occurring here. Because we are directing calls to FileRead, input() itself is not having a return type and value. So, an expression like n: i32 = i32(int(input("Enter a number: ")))) leads to an exception. A simple program:

name: str = input("Your name: ")
print("Hello,", name)

gives the following output

(base) saurabh-kumar@Awadh:~/Projects/System/lpython$ ./src/bin/lpython ./examples/example.py
Your name: Segmentation fault (core dumped)

I request you to see if the implementation is correct. Instead of a separate function create_Input() with a call inside if (call_name == "input"), I am using the complete piece of code here.

[Shaikh-Ubaid]

@kmr-srbh the following works:

% cat examples/expr2.py 
name: str = "                "
name = input("Your name: ")
print("Hello,", name)
% python examples/expr2.py
Your name: John
Hello, John
% lpython examples/expr2.py
Your name: John
Hello,John

We just needed name to have initial length/space so that we could write to it the string read from stdin.

[Shaikh-Ubaid]

We need to see what other better alternative approaches can be for the workaround (for name length) in #2655 (comment).

[kmr-srbh]

We need to see what other better alternative approaches can be for the workaround (for name length) in #2655 (comment).

You are right @Shaikh-Ubaid. How do we go about working a fix for the return type issue? This is a real problem. I am new to this area of the code-base and learning.

[certik]

Let's modify the semantics of the FileRead ASR node: if the "value" expr argument is an allocatable string, then the backend (LLVM/WASM, etc.) implementation of the FileRead node will allocate the string to hold the whole input, and assign it to it.

[kmr-srbh]

Let's modify the semantics of the FileRead ASR node: if the "value" expr argument is an allocatable string, then the backend (LLVM/WASM, etc.) implementation of the FileRead node will allocate the string to hold the whole input, and assign it to it.

@certik Do you mean handling String_t here?

lpython/src/libasr/codegen/asr_to_llvm.cpp

Lines 7493 to 7510 in fce0b35

	if (ASRUtils::is_array(type)) {
	if (ASR::is_a<ASR::Allocatable_t>(*type)
	|| ASR::is_a<ASR::Pointer_t>(*type)) {
	tmp = CreateLoad(tmp);
	}
	tmp = arr_descr->get_pointer_to_data(tmp);
	if (ASR::is_a<ASR::Allocatable_t>(*type)
	|| ASR::is_a<ASR::Pointer_t>(*type)) {
	tmp = CreateLoad(tmp);
	}
	llvm::Value *arr = tmp;
	ASR::ttype_t *type32 = ASRUtils::TYPE(ASR::make_Integer_t(al, x.base.base.loc, 4));
	ASR::ArraySize_t* array_size = ASR::down_cast2<ASR::ArraySize_t>(ASR::make_ArraySize_t(al, x.base.base.loc,
	x.m_values[i], nullptr, type32, nullptr));
	visit_ArraySize(*array_size);
	builder->CreateCall(fn, {arr, tmp, unit_val});
	} else {
	builder->CreateCall(fn, {tmp, unit_val});