# So surprised syntax error not caught here

**URL:** <https://www.ruby-forum.com/t/so-surprised-syntax-error-not-caught-here/115487>\
**Category:** Ruby\
**Created:** [September 25, 2007, 6:49pm UTC](https://www.ruby-forum.com/t/so-surprised-syntax-error-not-caught-here/115487 "2007-09-25T18:49:40Z")\
**Posts on this page:** 5\
**Page:** 1

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**Author:** ![winterheat](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/w/7993a0/32.png) [@winterheat](https://www.ruby-forum.com/u/winterheat)\
**Post date:** [September 25, 2007, 6:49pm UTC](https://www.ruby-forum.com/t/so-surprised-syntax-error-not-caught-here/115487/1 "2007-09-25T18:49:40Z")

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the following syntax error for “elif” is not caught? (should be elsif)

def foo(i)  
if i \< 0  
return “Less than 0”  
elif i == 0  
return “it is zero”  
else  
return “Greater than 0”  
end  
end

p foo(-2)  
p foo(0)  
p foo(10)

==================  
Output:

“Less than 0”  
“Greater than 0”  
“Greater than 0”

---

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**Author:** ![winterheat](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/w/7993a0/32.png) [@winterheat](https://www.ruby-forum.com/u/winterheat)\
**Post date:** [September 25, 2007, 6:59pm UTC](https://www.ruby-forum.com/t/so-surprised-syntax-error-not-caught-here/115487/2 "2007-09-25T18:59:14Z")

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From: removed\_email\_address@domain.invalid [[mailto:removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid)] On Behalf  
Of  
SpringFlowers AutumnMoon  
Sent: Tuesday, September 25, 2007 7:50 PM

> end  
> end

Rewrite indents this way to understand:

def foo(i)  
if i \< 0  
return “Less than 0”  
elif i == 0  
return “it is zero”  
else  
return “Greater than 0”  
end  
end

The “problem line” is parsed as

elif(i == 0)

Interpreter doesn’t complain on non-existent “elif” methods, because the  
line just never evaluated.

V.

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<div class="post-metadata">

**Author:** ![winterheat](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/w/7993a0/32.png) [@winterheat](https://www.ruby-forum.com/u/winterheat)\
**Post date:** [September 25, 2007, 7:00pm UTC](https://www.ruby-forum.com/t/so-surprised-syntax-error-not-caught-here/115487/3 "2007-09-25T19:00:15Z")

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On 9/25/07, SpringFlowers AutumnMoon [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid) wrote:

> end
> 
> p foo(-2)  
> p foo(0)  
> p foo(10)

It’s treating “elif” as a (possible) method call that’s never reached  
because of the “return”. You don’t need “return” for what you have:

def foo(i)  
if i \< 0  
“Less than 0”  
elif i.zero? # i == 0  
“Equal to 0”  
else  
“Greater than 0”  
end  
end

That will fail, but not with a syntax error. (It should fail with an  
UnknownMethod.) Ruby is expression-oriented, and the last expression  
executed in the execution path is returned from the execution path.

-austin

---

<div class="post-metadata">

**Author:** ![winterheat](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/w/7993a0/32.png) [@winterheat](https://www.ruby-forum.com/u/winterheat)\
**Post date:** [September 25, 2007, 7:06pm UTC](https://www.ruby-forum.com/t/so-surprised-syntax-error-not-caught-here/115487/4 "2007-09-25T19:06:16Z")

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SpringFlowers AutumnMoon wrote:

> the following syntax error for “elif” is not caught? (should be elsif)
> 
> def foo(i)  
> if i \< 0  
> return “Less than 0”  
> elif i == 0  
> return “it is zero”

Ruby is interpretive; it does not link all its symbols to real  
entities at compile time. (Unlike certain other languages we could  
mention.

elif could be a function that takes a boolean. Ruby can’t know this  
until it interprets the line, because you might have used eval() or  
something to create that function before getting here.

In exchange for a lot more flexibility, Ruby does fewer sanity checks  
at parse time.

To keep Ruby on track, and catch errors like this, all Ruby developers  
should write unit tests for everything.

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<div class="post-metadata">

**Author:** ![winterheat](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/w/7993a0/32.png) [@winterheat](https://www.ruby-forum.com/u/winterheat)\
**Post date:** [September 27, 2007, 12:37am UTC](https://www.ruby-forum.com/t/so-surprised-syntax-error-not-caught-here/115487/5 "2007-09-27T00:37:45Z")

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Austin Z. wrote:

> ```
> "Greater than 0"
> * removed_email_address@domain.invalid * http://www.halostatue.ca/feed/
> * removed_email_address@domain.invalid
> 
> ```

My word, you have just given me a reason to stop using returns !!!

It doesn’t hurt code readability to go by syntax rather then insert the  
“Yes  
Mr/Miss Programmer don’t forget we return here” return statements  
through out  
code ether.

TerryP.