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author | Marti Bolivar <mbolivar@mit.edu> | 2010-12-03 20:18:00 -0500 |
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committer | Marti Bolivar <mbolivar@mit.edu> | 2010-12-03 20:18:00 -0500 |
commit | 5ceac644e90c929e77f05d357d1d35d45e673fac (patch) | |
tree | 18c76f6117942fa46391fbbd8bd24e2c759c4895 /docs/source/lang/comparison.rst | |
parent | e5b1e44a8ae8c593456f4b4734f05c9065f6f07b (diff) | |
download | librambutan-5ceac644e90c929e77f05d357d1d35d45e673fac.tar.gz librambutan-5ceac644e90c929e77f05d357d1d35d45e673fac.zip |
cleaning up previous commits.
note that addition of new files under docs/source/lang/api and
docs/source/lang/cpp which were just copies of files in
docs/source/lang/ imply that change history is lost to git.
Diffstat (limited to 'docs/source/lang/comparison.rst')
-rw-r--r-- | docs/source/lang/comparison.rst | 87 |
1 files changed, 0 insertions, 87 deletions
diff --git a/docs/source/lang/comparison.rst b/docs/source/lang/comparison.rst deleted file mode 100644 index b24355f..0000000 --- a/docs/source/lang/comparison.rst +++ /dev/null @@ -1,87 +0,0 @@ -.. highlight:: cpp - -.. _lang-comparison: - -Comparison Operators (``==``, ``!=``, ``<``, ``>``, ``<=``, ``>=``) -=================================================================== - -The comparison operators ``==``, ``!=``, ``<``, ``>``, ``<=``, and -``>=`` are used to compare two numbers. They are :ref:`true -<lang-constants-true>` when the comparison is true, and :ref:`false -<lang-constants-false>` otherwise. They are based on the symbols -=, ≠, <, >, ≤, and ≥ from mathematics. - -Here are some examples, with their meaning in comments:: - - // "eq" is true when x is equal to y - bool eq = (x == y); - - // "neq" is true when x is different than y - bool neq = (x != y); - - // "lt" is true when x is less than, but NOT equal to, y - bool lt = (x < y); - - // "gt" is true when x is greater than, but NOT equal to, y - bool gt = (x > y); - - // "lte" is true when x is less than or equal to y - bool lte = (x <= y); - - // "gte" is true when x is greater than or equal to y - bool gte = (x >= y); - -The parentheses are optional; they are present only for clarity. For -example, the following two lines are the same:: - - bool eq = x == y; - - bool eq = (x == y); - -Uses ----- - -Comparison operators, along with :ref:`boolean operators -<lang-boolean>`, are useful inside the conditionals of :ref:`if -<lang-if>` statements. Here's one example:: - - if (x < 50) { - // only execute these lines if x is less than 50 - SerialUSB.println("delaying:"); - SerialUSB.println(x); - delay(x); - } - -.. warning:: - Beware of accidentally using the single equal sign (``=``) when you - meant to test if two numbers are equal (``==``). This is a common - mistake inside of ``if`` statement conditionals, e.g.:: - - // DON'T MAKE THIS MISTAKE - if (x = 10) { - // body - } - - The single equal sign is the assignment operator, and sets x to 10 - (puts the value 10 into the variable x). Instead use the double equal - sign (e.g. ``if (x == 10)``), which is the comparison operator, and - tests *whether* x is equal to 10 or not. The latter statement is only - true if x equals 10, but the former statement will always be true. - - This is because C evaluates the statement ``if (x=10)`` as follows: 10 - is assigned to x (remember that the single equal sign is the - :ref:`assignment operator <lang-assignment>`), so x now - contains 10. Then the 'if' conditional evaluates 10, which evaluates - to :ref:`true <lang-constants-true>`, since any non-zero number - evaluates to ``true``. - - Consequently, the conditional of an ``if`` statement like ``if (x = - 10) {...}`` will always evaluate to ``true``, and the variable x - will be set to 10, which is probably not what you meant. - - (This sometimes has uses, though, so just because an assignment - appears within a conditional doesn't mean it's automatically wrong. - Be careful to know what you mean.) - - -.. include:: cc-attribution.txt |