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--- buzz_syntax_cheatsheet [2016/04/09 22:02] – root
+++ buzz_syntax_cheatsheet [2018/03/23 18:17] (current) – jayam
@@ Line 1: / Line 1: @@
+====== Buzz Syntax Cheatsheet ======
+^ Category ^ Examples ^
+^ Comments | <code buzz># This is a comment</code> |
+^ File inclusion | <code buzz>include "otherfile.bzz"
+# NOTE: A specific file can be included only once.
+# Any 'include' statement for a file is ignored after the first inclusion
+# occurred.
+# Relative paths are automatically transformed into absolute paths before
+# including a file.</code>|
+^ Variables | <code buzz># assignment (by default variables are global)
+x = 2.55   # number
+x = "ciao" # string
+# local variables
+function f() {
+   var x = 42
+   # do stuff with x
+}
+# printing on the ARGoS logger
+log("INFO: x = " , x)</code> |
+^ Conditionals | <code buzz># simple if/then
+if (x > 3) {
+   log("x is too big")
+}
+# if/else
+if (x > 3)
+   log("x is too big")
+else if (x < 3)
+   log("x is too small")
+else
+   log("maybe I just don't like x")
+# checking for equality
+if x == 3
+   log("x is equal to 3")
+# checking for inequality
+if (x != 4)
+   log("x is different from 4")
+# combining conditions with OR
+if (x < 3) or (x > 3)
+   log("x is not 3")
+# combining conditions with AND
+if ((x > 3) and (y > 3))
+   log("x and y are too big")
+# negating a condition
+if (not (x < 3))
+   log("x is <= 3")</code> |
+^ Loops |<code buzz># 'while' loop to print 1 2 3 4 5
+x = 0
+while (x < 5) {
+   x = x + 1
+   log(x)
+}</code> |
+^ Tables |<code buzz># creating an empty table
+t = {}
+# creating a table with some initial value
+t = { .x=3 }
+# using the contents of a table: two equivalent ways
+log("t.x = ", t.x)       # dot syntax
+log("t['x'] = ", t["x"]) # string syntax
+# printing the contents of a table: a custom function
+function table_print(t) {
+  foreach(t, function(key, value) {
+      log(key, " -> ", value)
+    })
+}
+# tables are always passed by reference!
+t1 = { .x=3 }
+t2 = t1      # now t2 points to the contents of t1 -> no deep copy
+t2.x = 5
+log(t1.x)    # prints 5, not 3!
+# copying tables the right way
+function table_copy(t) {
+  var t2 = {}
+  foreach(t, function(key, value) {
+      t2[key] = value
+    })
+  return t2
+}
+t1 = { .x=3 }
+t2 = table.copy(t1)
+t2.x = 5
+log(t1.x)    # prints 3
+log(t2.x)    # prints 5
+# prints the number of elements in a
+log(size(a))</code> |
+^ Functions |<code buzz># defining a function
+function my_fun(p) {
+   log("Called my_fun(", p, ")")
+}
+# returning a value
+function my_add(a, b) {
+   return a + b
+}
+# creating a lambda
+lambda = function(a, b) {
+   return a + b
+}
+lambda(1,2)</code> |
+^ Math |<code buzz># all the math functions are part of the 'math' table
+# setting a 2D vector from length and angle
+function vec2_new_polar(length, angle) {
+   var vec2 = {
+      x = length * math.cos(angle)
+      y = length * math.sin(angle)
+   }
+   return vec2
+}
+v = vec2_new_polar(2, math.pi/3)
+# Summing two 2D vectors (v1 = v1 + v2)
+function vec2_sum(v1, v2) {
+   v1.x = v1.x + v2.x
+   v1.y = v1.y + v2.y
+}
+v1 = { .x=1, .y=2 }
+v2 = { .x=3, .y=1 }
+vec2_sum(v1, v2)
+# Getting the angle of a 2D vector
+function vec2_angle(v) {
+   return math.atan(v.y, v.x)
+}</code> |
+^ Swarm management |<code buzz># creation of a swarm with identifier 1
+s = swarm.create(1)
+# Join the swarm if the robot identifier (id) is even
+# - 'id' is an internal symbol that refers to the
+#   numeric id of the robot executing the script
+# - % is the modulo operator
+s.select(id % 2 == 0)
+# Join the swarm unconditionally
+s.join()
+# Leave the swarm if the robot id is greater than 5
+s.unselect(id > 5)
+# Leave the swarm unconditionally
+s.leave()
+# Check whether a robot belongs to s
+if(s.in()) { ... }
+# Assigning a task to a swarm
+s.exec(function() { ... })
+# a, b are swarms defined earlier in the script
+# Create new swarm with robots belonging to both a and b
+# The first argument is a unique swarm identifier
+i = swarm.intersection(100, a, b)
+# Create new swarm with robots belonging to a or b
+u = swarm.union(101, a, b)
+# Create new swarm with robots belonging to a and not to b
+d = swarm.difference(102, a, b)
+# Create a new swarm n as the negation of swarm s
+n = s.others(103)</code> |
+^ Neighbor management | <code buzz># Iteration (rid is the neighbor's id)
+neighbors.foreach(
+  function(rid, data) {
+    log("robot ", rid, ": ",
+        "distance  = ", data.distance, ", ",
+        "azimuth   = ", data.azimuth, ", ",
+        "elevation = ", data.elevation) })
+# Transformation
+cart = neighbors.map(
+  function(rid, data) {
+    var c = {}
+    c.x = data.distance * math.cos(data.elevation) *
+          math.cos(data.azimuth)
+    c.y = data.distance * math.cos(data.elevation) *
+          math.sin(data.azimuth)
+    c.z = data.distance * math.sin(data.elevation)
+    return c
+  })
+# Reduction (accum is a table)
+# with values x, y, and z, initialized to 0
+result = cart.reduce(function(rid, data, accum) {
+    accum.x = accum.x + data.x
+    accum.y = accum.y + data.y
+    accum.z = accum.z + data.z
+    return accum
+  }, {.x=0, .y=0, .z=0})
+# Filtering
+onemeter = neighbors.filter(function(rid, data) {
+    # We assume the distance is expressed in centimeters
+    return data.distance < 100 })
+# Listening to a (key,value) pair
+neighbors.listen("key",
+   function(vid, value, rid) {
+      log("Got (", vid, ",", value, ") from robot #", rid)
+   }
+)
+# Stopping listening to a key
+neighbors.ignore("key")
+# Broadcasting a (key,value) pair
+neighbors.broadcast("key", value)</code> |
+^ Virtual stigmergy | <code buzz># Create a new virtual stigmergy
+# A unique id (1 here) must be passed
+v = stigmergy.create(1)
+# Write a (key,value) entry into the structure
+v.put("a", 6)
+# Read a value from the structure
+x = v.get("a")
+# Get the number of keys in the structure
+log("The vstig has ", v.size(), " elements")</code> |