Just checking

if I have

a = a - b*c

b*c gets calculated first then that result is subtracted from a ?

In other words, parantheses, in Ruby, is not necessary to make that

calculation ?

TIA

Stuart

Just checking

if I have

a = a - b*c

b*c gets calculated first then that result is subtracted from a ?

In other words, parantheses, in Ruby, is not necessary to make that

calculation ?

TIA

Stuart

On Jun 30, 2006, at 12:07 PM, Dark A. wrote:

TIA

Stuart

irb says yes:

irb(main):001:0> 2 - 3 * 5

=> -13

-Mat

On 6/30/06, Dark A. [email protected] wrote:

Just checking

if I have

a = a - b*c

b*c gets calculated first then that result is subtracted from a ?

In other words, parantheses, in Ruby, is not necessary to make that

calculation ?

It’s best to check this sort of thing in irb.

-austin

If you have pickaxe2, look at page 339.

Most languages that have expressions like this know the typical order

of operation for things that come from the world of math.

Be careful with this since - and * can be redefined based on the

classes they’re operating on:

a = %w(h t h h h t t t h h t h)

=> [“h”, “t”, “h”, “h”, “h”, “t”, “t”, “t”, “h”, “h”, “t”, “h”]b = [ “h” ]

=> [“h”]c = 7

=> 7a = a - b*c

=> [“t”, “t”, “t”, “t”, “t”]

-Rob

On Sat, 1 Jul 2006, Dark A. wrote:

TIA

Stuart

My Dear Aunt Sally

1 - multiply

2 - divide

3 - add

4 - substract

regards.

-a

On Jun 30, 2006, at 11:07 AM, Dark A. wrote:

Just checking

if I have

a = a - b*c

b*c gets calculated first then that result is subtracted from a ?

That’s right. Just like normal math rules.

In other words, parantheses, in Ruby, is not necessary to make that

calculation ?

As long as that’s what you want, yes.

James Edward G. II

On Jun 30, 2006, at 12:07 PM, Dark A. wrote:

TIA

Stuart

Yes. Ruby has the usual precedence rules for arithmetic operators.

Agreed , sorry.

Stuart

Dark A. wrote:

Just checking

if I have

a = a - b*c

In other words, parantheses, in Ruby, is not necessary to make that

calculation ?

Ruby uses pretty much the same precedence rules as C. Se p. 221 in the

PickAxe 1st Ed., for example.

Just checking

if I have

a = a - b*c

In other words, parantheses, in Ruby, is not necessary to make that

calculation ?

Table of ruby operators and their precedence:

http://phrogz.net/ProgrammingRuby/language.html#table_18.4

----- Original Message ----

From: [email protected]

To: ruby-talk ML [email protected]

Sent: Friday, June 30, 2006 3:23:35 PM

Subject: Re: Order of precedence

On Sat, 1 Jul 2006, Dark A. wrote:

TIA

Stuart

My Dear Aunt Sally

1 - multiply

2 - divide

3 - add

4 - substract

regards.

-a

On 6/30/06, Rob B. [email protected] wrote:

a = %w(h t h h h t t t h h t h)

=> [“h”, “t”, “h”, “h”, “h”, “t”, “t”, “t”, “h”, “h”, “t”, “h”]b = [ “h” ]

=> [“h”]c = 7

=> 7a = a - b*c

=> [“t”, “t”, “t”, “t”, “t”]

Keep in mind that Array#- does setlike operations:

[:h] * 1000 - [:h] #=> []

So the number of h’s above Just Doesn’t Matter.

wow, while I’ve been using irb for some things, I am now a true

believer.

I have been struggling to understand a calculation in some code .

Checking the calc in my head.

It made me forget an important Ruby and probably all programming

languages rule.

Here is the code:

left = 22

write = left/10 # I’m was thinking should return 2.2, but no it

returns just 2 (no modulus)

left = left - write*10 # based on the wrong head calculation above it

was not allowing me to

# what this value truly is.

Well, lesson learned.

Stuart

[email protected] writes:

calculation ?

regards.

## -a

suffering increases your inner strength. also, the wishing for suffering

makes the suffering disappear.

- h.h. the 14th dali lama

Actually more like

1 - multiply and divide

2 - add and subtract

Steve

My Dear Aunt Sally

I was taught a close variant:

Please Excuse My Dear Aunt Sally

1 - Parenthesis

2 - Exponentiation

3 - Multiply

4 - Divide

5 - Add

6 - Subtract

BODMAS

Brackets

Other (powers etc)

Division

Multiply

Add

Subtract

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