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Why do most languages use right-to-left assignments? Is it purely a matter of path dependence? I guess also that binding a value to a name usually indicates tha

Why do most languages use right-to-left assignments? Is it purely a matter of path dependence? I guess also that binding a value to a name usually indicates that you'll use the name later on, and having the name on the LHS makes for a better UI for looking up the value the name is bound to. On an unrelated side note, I've always thought "=" was a huge mistake in language design, confusing countless people who are coming into programming who reasonably mistake it for equality. I don't know why it won over ALGOL-style ":=".

dragonwriter 6y ago
> On an unrelated side note, I've always thought "=" was a huge mistake in language design, confusing countless people who are coming into programming who reasonably mistake it for equality. I don't know why it won over ALGOL-style ":=". Probably because adding a colon to an equality sign doesn’t clarify the meaning at all. Had Algol (as some less widely influential for other reasons languages have) adopted something that more clearly represented movement into the variable being assigned like: a <- 25 Maybe it would have won out over “=" for assignment.
- lioeters 6y ago
  I considered such an assignment operator for a little language I was developing, but there was an ambiguity between this: a <- 25 and this: a < -25 Since everything was an expression in the language, the latter would evaluate to a boolean. In the end I just went with "=" for assignment, and "==" for equality.
rowanG077 6y ago
"=" is still equality. It's not an operator that compares two values. It's an operator that defines the left hand to be equal to the right hand. I feel like "=" for assignment is fine. For boolean comparison something like "=?" seems most clear, like asking a question whether the left and right hand side are equal.
- scarmig 6y ago
  In imperative languages, assignment has a side effect of making the LHS equal to the RHS. But it's still different from equality, since variables can be reassigned E.g. a = 2 a = 3 2 = 3 //what??? Assignment is fundamentally part of the language execution model, which is entirely apart from anything related to mathematical equality. Even in languages where you can't rebind a variable name, it's still weird to use = as assignment, since it would have such different behavior than seemingly analogous operators like > and <.

dragonwriter 6y ago

> On an unrelated side note, I've always thought "=" was a huge mistake in language design, confusing countless people who are coming into programming who reasonably mistake it for equality. I don't know why it won over ALGOL-style ":=". Probably because adding a colon to an equality sign doesn’t clarify the meaning at all. Had Algol (as some less widely influential for other reasons languages have) adopted something that more clearly represented movement into the variable being assigned like: a <- 25 Maybe it would have won out over “=" for assignment.

lioeters 6y ago
I considered such an assignment operator for a little language I was developing, but there was an ambiguity between this: a <- 25 and this: a < -25 Since everything was an expression in the language, the latter would evaluate to a boolean. In the end I just went with "=" for assignment, and "==" for equality.

rowanG077 6y ago

"=" is still equality. It's not an operator that compares two values. It's an operator that defines the left hand to be equal to the right hand. I feel like "=" for assignment is fine. For boolean comparison something like "=?" seems most clear, like asking a question whether the left and right hand side are equal.

scarmig 6y ago
In imperative languages, assignment has a side effect of making the LHS equal to the RHS. But it's still different from equality, since variables can be reassigned E.g. a = 2 a = 3 2 = 3 //what??? Assignment is fundamentally part of the language execution model, which is entirely apart from anything related to mathematical equality. Even in languages where you can't rebind a variable name, it's still weird to use = as assignment, since it would have such different behavior than seemingly analogous operators like > and <.